A Study of Vasomotor Responses Following upon Experimental Lesions of the Brain Stem *

It is believed that the sympathetic nervous system through its peripheral distribution, and possibly through central connections, exerts, at least' in part, a control on vasomotor tonus. In recent years, several series of experiments on dogs have been conducted in this laboratory to determine the course of vasomotor fibers as measured by thermic changes in the feet after arterial ligation and section of the spinal cord at various levels.0"1 The occurrence of vasodilatation in the dog's foot was observed after hemisection or transection of the spinal cord at a level as high as C-1. It seemed advisable subsequently to investigate the possibility of a central vasomotor regulatory mechanism, and to fix, if possible, the locus of control of this particular phenomenon. Furthermore, it seemed important to consider two other functions;--the r8le of arterial blood pressure changes, and the r8le of body temperature changes in connection with peripheral temperature manifestations induced by sympathetic nervous system control. The present communication is a report on the approach which has been made to these problems.